Despite the fact that I have Height="100%" specified, the ReportViewerWebPart is not expanding to take up 100% of the view. Has anyone seen this behavior and if so, is there any workaround. I'm using Assembly="Microsoft.ReportingServices.SharePoint.UI.WebParts,Version=10.0.0.0".

Hey, it seems to be the WebPart itself. The container fills the space, but the web part does not.
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Daniel J. SeganJan 5 '11 at 22:19

If the content inside the webpart isn't expanding, wouldn't the actual RDL need to be modified? It is hard to debug without actually looking at it so I would recommend using Firebug + Firefox to inspect.
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Kit MenkeJan 6 '11 at 14:29

I solved this once using a custom webpart that loaded a custom javascript file on pages where the report service webparts resides (requires jQuery). The following snippet is a bit old and might contain requirements not eligible to yours but you should get the point: